Direct conversion detectors and detector arrays are utilized in medical imaging in order to convert x-ray photons directly into electric charges. They are typically comprised of an x-ray photoconductor layer grown directly on top of the charge collector and readout layer (such as room temperature semi-conductors). The detectors are commonly utilized in arrays of multiple detector (or tiles) such that an increased image size with improved resolution may be generated.
The performance of the detectors, especially the peripheral detector elements, can be important to many imaging applications. The linearity, uniformity, stability, and consistency can be especially important for peripheral detectors. For many applications, such as mammography chest wall dead space, the requirements of imaging can be very stringent. For tiled imaging detectors built with room temperature semiconductors, the edges of each tile can cause significant non-uniformity or visible artifacts. This is known to arise due to the much higher leakage current and distorted electric field near the edges. Artifacts around the edges of the tiles may be highly undesirable. These artifacts are believed to be caused by the degraded performance of the edge pixels. These artifacts become roadblocks for the implementation of these detectors and detector arrays in medical imaging applications where line artifacts are prohibited.
It is known that a guard ring may be utilized to improve peripheral pixel behavior. Know configurations manufacture the guard ring on the same surface of the pixellated side of the detector and apply the same potential as its neighbor, i.e. ground. Therefore, the electric field distortion to the edge pixels is reduced or eliminated depending on the size of the guard ring. Furthermore, side wall leakage current is collected by the guard ring and has no impact on the edge pixels. However, these co-planar guard rings generate an inactive spatial region with a dimension of the guard ring geometry. This is undesirably for tiled detector boundaries or detector edges which can have a very limited tolerance to inactive space. Thus existing guard ring designs may also be unsuitable for medical imaging applications wherein line artifacts due to the inactive space may be unacceptable.
It would, therefore, be highly desirable to have a direct conversion detector with improved edge pixel performance. It would additionally be highly desirable to have a direct conversion detector array with reduced artifacts and reduced inactive space characteristics.